The invention is related to a system for charging for the use of a packet-based telecommunication network, such as an ATM or IP oriented network.
a. ATM (Asynchronous Transfer Mode)
ATM (Asynchronous Transfer Mode) is a relatively new network technique for supplying connections with very different characteristics in a uniform manner. Each ATM connection has to be paid. Preferably, the amount charged for the connection reflects both the performance delivered by the network and the performance experienced by the customer. In a telephone network such as this, an amount charged is determined by letting the amount be dependent on the duration of the connection (calculated in seconds, minutes or other units, such as “ticks”) and on the distance covered. A telephone call is almost always a case of a connection with a fixed capacity (e.g., 64 kbit/s with ISDN). In contrast, ATM is much more flexible and there are more connection parameters and variables than with PSTN (Public Switched Telephone Network) or ISDN (Integrated Services Digital Network) based connections.
With ATM, connections can be established with varying capacity (some kbit/s up to hundreds of Mbit/s).
With ATM, connections can be established with varying network guarantees concerning cell loss, cell delay, cell delay variance and throughput by choosing an “ATM Transfer Capability” (ATC) and Quality of Service class (QoS class). The amount charged for an ATM connection should preferably also reflect this additional flexibility, which is the subject of the present invention. An important aspect in determining the manner of charging for ATM connections is the direction (incentive) that the charging gives to the manner of network usage. In a traditional telephone network, the time-related charge usually assures that the customer does not unnecessarily occupy the connection. In a traditional data network usually a volume rate is used, so that there is an incentive not to burden the network with unnecessary traffic. Another example is the application of an off-peak rate with a plan to shift a portion of the network traffic to periods outside the peak hours so that the network can have a smaller configuration and is thereby less expensive.
The present state of the art usually envisages basing the charge of an ATM connection on two variables, i.e., a time component, the duration of time of the connection (session), and a volume component, the total number of ATM cells transmitted and/or received during the connection. Both variables can easily be measured, registered and processed into a charge during the connection. On processing of the values of the time component, the price per unit can depend on various quantities. Examples of such quantities are the distance covered and time of the day or of the week, comparable with the usual charging for telephone. Examples of other quantities are the ATM parameters such as the Peak Cell Rate of the connection, etc.
There are different ATCs standardized in ITU-T recommendation I.371. Hereafter the limitations for some of the ATCs of choosing a charge that is based on the time and volume component are indicated as described above.
A charge which is exclusively based on the time and volume component as set out in the above, has as a consequence that only the total connection duration and only the total number of cells during the duration of the connection play a role in the charge. For these quantities, (and thereby for the charge) it does not matter whether all cells are offered evenly over the connection duration (“Constant Bit Rate”) or are concentrated in one or more bursts of cells (“Variable Bit Rate”). For the network, it is advantageous if the cells offered are spread as much as possible. ATM connections that use SBR (Statistical Bit Rate) are characterized by two additional parameters, the Sustainable Cell Rate (SCR) and the Maximum Burst Size (MBS). The essence of the situation set out above does not change; however, the user experiences no incentive to spread the cells as evenly as possible. While this is beneficial for the total network capacity and consequentially is pursued by the network operator, the question is, in which way can the user can be urged to offer the traffic as evenly as possible. In other words, a method is needed to urge the network user via the charging mechanism to offer the traffic in a less bursty way. If in an ATM network, use is made of an ABR (Available Bit Rate) control mechanism, the network dynamically assigns capacity to each connection. However, it can occur that the network assigns capacity to a connection but that the user does not use or completely use all that capacity, e.g., if the user sends less cells than the assigned capacity allows. With the present charging mechanisms (based on a total time and a total volume component in the charge), leaving capacity assigned by the network unused leads to a lower charge. There is no incentive to use the assigned capacity indeed and there is no incentive to gear the capacity to the actual current need.
b. IP (Internet Protocol)
The IP (Internet Protocol) is a connectionless packet switched technique that is used for the Internet. Current IP networks exclusively supply a so-called best-effort service. The network commits itself to make an effort to deliver the packet (datagram) at the destination but no guarantee is given; the packet can be lost in case of a congestion. It is customary to charge access to the Internet only, e.g., by a fixed amount per month (flat rate) or by a fixed rate per unit of time (hour) that the user is logged onto an Internet Service Provider. In this type of charging, there is no relationship with the amount of data that a user asks or offers.
Because IP is a connectionless technique, there is no matter of “connections” in the same sense as with a telephone or an ATM connection. The aspect of time is therefore inherently unsuitable to serve as measure for network load. To be able to relate the use of an IP network to the network load caused by the network user, another quantity has to be used.
The amount of data can be expressed in different IP units, such as the number of datagrams per unit IP of time and the number of bytes (or bits) per unit of time of which the datagrams consist.
c. Guaranteed IP Services
Recently, work has been done on an extension of the services that an IP network can offer. The aim is, next to the best-effort service described in the above, to also enable an IP network to give guarantees for the throughput and for the delay experienced in the network, comparable with the possibilities that an ATM network offers. The standardization of these new services with guarantees is still in an early stage.
One of the proposed possibilities is to use reservations, e.g., with the protocol RSVP. In that case, it is desirable that the extent of the reservation requested or made and the duration of the reservation is expressed in the charge.
In another proposed approach, some bits in the IP header are used to indicate to which service class the IP packet belongs, e.g., “best-effort” or “guaranteed with short delay”. In that case, it is desirable that the indication of the service class also is expressed in the charge.
All considerations as mentioned above for ATM/ABR and ATM/SBR are mutatis also applicable on these new IP services with guarantees.